Find out what a couple more hours could do for your body

Wake up! You cannot justify sleeping less than 7 hours a night. Dowsing yourself in coffee every morning may get you through the day, but habitually cutting corners on your sleep means you’re not only blunting health benefits but cutting years off your life.

“There’s more consequences to insufficient sleep than just feeling groggy the next day, and I think a lot of people don’t realize that. They’re like, ‘Well, if I can power through the day, then it was enough,’” says Michael Grandner, PhD, a clinical psychologist and instructor of psychology at the University of Pennsylvania. “But there’s a lot more going on.” Here’s what:

If nothing else will motivate you to get more shuteye, this should be it: Sleep keeps the weight off—not just for vanity but also for health.

Lack of sleep can lead to more of both midnight and midday munching. It turns out that sleep deprivation triggers higher levels of a hunger-inducing molecule that increased appetite during the afternoon, according to research presented at The Endocrine Society’s Annual Meeting this year. But the mindless munching doesn’t stop there.

It turns out the longer you’re awake, the more opportunities there are for you to snack. Researchers reported in the journal Sleep that those who slept less and later at night had a much higher caloric intake than those who slept at 10 PM and got a full night’s sleep. Even worse, food consumed at night had a higher percentage of calories from fat than all three other meals of the day.

“One life style change that people could make if they’re either trying to lose weight or just trying to maintain their weight would be to really try to go to bed around 10 PM,” says Andrea Spaeth, lead author of the study. “That would really prevent a lot of people from consuming extra calories when they’re snacking late at night.”

2. Sleep improves your decision-making abilities.

Let’s be real here—when you’re struggling to even keep your eyes open your judgment isn’t at its peak performance.

The tendency to throw reason to the wayside has to do with a lack of impulse control induced by sleep deficiency, says Matthew P. Walker, PhD, an associate professor of psychology and neuroscience at the University of California, Berkeley. It weakens the connection between the amygdala, the part of the brain that regulates emotions, and the prefrontal cortex, the part that makes most high-level decisions for the body.

“If the amygdala is the gas pedal of your emotions, then the prefrontal cortex is the break,” Dr. Walker says. “When you are sleep-deprived, that connection between those two areas is sort of severed, and as a consequence, you become imbalanced. You become all gas pedal and no break.”

3. Sleep decreases anxiety.

The sleep-deficient human brain actually mirrors that of a person with an actual psychological disorder when faced with negative situations, according to a study published in the Journal of Neuroscience.

“It’s almost as if the brain was having a disproportionately increase or an exaggerated response to something bad when you’re sleep deprived,” says Dr. Walker.

During deep REM sleep, the brain is able to “reset those emotional settings” and refresh the mind, similar to how one might reboot a computer when it’s acting up. Your brain needs that downtime to digest all the emotions from the previous day.

4. Sleep refreshes your immune system.

The idea that sleep resets your brain doesn’t just apply to the brain, but also to the immune system, which fights infections by day but reorganizes itself and replaces dead cells by night. This is because the entire body—down to each teeny, tiny cell—operates on a 24-hour clock, says Gianluigi Mazzoccoli, MD, director of the Scientific Institute and Regional General Hospital (Casa Sollievo della Sofferenza) in Italy.

“Day and night are characterized by completely different spectra of physiological functions,” Dr. Mazzoccoli says. “And the immune system is absolutely directed by these distinctions of periods.”

5. Sleep stabilizes blood sugar.

In general, shorter sleepers tend to have a higher risk of diabetes. When studying a small group of normal sleepers, researchers in Los Angeles found that even just three nights of “catch-up sleep” to make up for what was lost over the week resulted in a 31% improvement in insulin sensitivity, compared to those who continued to have poor sleep schedules.

6. Sleep lowers your risk of disease—period.

Every single expert we spoke with warned of the dangerous long-term effects associated with habitual inadequate sleep. Short sleepers tend to have higher cholesterol levels and blood pressure, and both of these tend to have higher rates of increasing 10 years down the line, alongside the elevated risk of various cardiovascular problems diabetes, and obesity already mentioned.

“An important thing that people need to remember is that sleep, like diet, is an important pillar of health,” Dr. Grandner says. “It is impossible to be in good health and have unhealthy sleep.”